Semiconductor image sensors are used for sensing light or radiation waves. Complementary metal-oxide-semiconductor (CMOS) image sensors (CIS) and charge-coupled device (CCD) sensors are widely used in various applications such as digital camera or mobile phone camera applications.
A back side illuminated (BSI) image sensor device is one type of image sensor device. Image pixels in the BSI image sensor device generate electrical signals in response to incident light. Magnitudes of the electrical signals depend on intensity and wavelengths of the incident light received by the respective image pixels. As the size of transistor devices shrinks with each technology generation, existing BSI image sensor devices may begin to suffer from issues related to dark current or optical crosstalk. One technique for these issues may be that of forming deep trench isolations in the substrate for sufficient isolation between neighboring image pixels. However, a loading effect may occur when forming the deep trenches.